refactoring and log improvement.
refactoring and log improvement.

[common]
  commonize GetID.
  move StartCyclicProc/WaitStopSignal from alice/charlie.
[logger]
  output handler-name when its called and returned.
  delete unnecessary fmt.Sprintf in logger.Println.
[error]
  use fmt.Errorf instead of errors.New

ElementsProject/confidential-assets-demo,ElementsProject/confidential-assets-demo,ElementsProject/confidential-assets-demo,ElementsProject/confidential-assets-demo